The My Week with Marilyn actor, who will play Marius in Tom Hooper's upcoming movie adaptation of the long-running musical, is said to have "dumped" Swift after she failed to be cast in the project.
Swift was in the running for the role of Eponine but lost out to Samantha Barks, a decision which is said to have ruined her secretly budding romance with Redmayne as he will be away filming the movie.
"They hung out in New York City with the movie's execs and Taylor developed feelings for him fast," a source told Us Weekly.
"Taylor loved the image of a British boyfriend. [But] Eddie's not interested in a long-distance relationship," the insider added. "The elements were against them. It's a shame."
Swift was recently rumoured to have shared a "flirty" dinner date with Zac Efron, though they are believed to only be close friends.
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Watch a clip of Eddie Redmayne talking to Digital Spy below: